Production of alpha, beta-dichlorpropionic acid esters



United rates PRODUCTION OF ALPHA,BETA-DICHLOR- PROPIONIC ACEDESTERS No Drawing. Application August 6, 1956, Serial No. 602,418

laims priority, application Germany ugust 11, 1955 6 Claims. (Cl. 260-487) This invention relates to animproved process for the production of dichlorpropionic acid esters by adding on chlorine to esters of acrylic acid in the vapor phase. In particular it relates to the production of dichlorpropionic acidesters in the vapor phase in the presence of new substances for promoting the reaction.

It is already known that alpha.beta-dichlorpropionic acid esters can be obtained by adding on chlorine to esters of acrylic acid. The reaction may be carried out in the liquid phase or in the vapor phase. Working in the: gas phase has in general the advantage that the reacti-on' proceeds more uniformly, less side reactions occur and the use of solvents or diluents is not necessary.

. One object of this invention is to improve the said method of working, to suppress further the side reactions and to increase the. yields of alpha.beta-dichlorpropionic acid: esters.

A further object is to facilitate the adding on of chlorine to acrylic acid esters in the vapor phase by the addition of substances which promote the reaction and thereby to achieve a substantially complete conversion.

We have found that the said objects can be achieved and the additive chlorination of acrylic acid estersin the gas phase can be improved by carrying out the reaction of the ester with chlorine in the presence of a minor amount, preferably of 0.1 to by weight, of at least one'nitrogenous compound of the type of N-substituted carboxylic acid amides or amines, with reference to the amount of acrylic acid ester used.

The additives are preferably chosen so that their boiling point does not deviate appreciably from that of the acrylic acid ester. This has the advantage that they can readily be vaporized with the acrylic acid ester, whereby not only their admixture with the acrylic acid ester and their introduction into the reaction zone, but also the working up of the. reaction product is simplified.

As N-substituted acid amides there are suitable in particular the amides of lower aliphatic carboxylic acids, in particular saturated monocarboxylic acids having 1 to 3 carbon atoms in the molecule, in which at least one hydrogen atom of the arnido group is replaced by an aliphatic radical, in particular an alkyl group with 1 to 4 carbon atoms in. the molecule. Suitable amides are for example, N-methylformamide, N.N-dimethylfortnamide, N.N-diethylformarnide, N-ethylformamide, N-butylforrnamide, N.N-dibutylformamide, N-methylacetamide and N-ethyla-cetamide. N-substituted cyclic amides, in particular those substituted by lower aliphatic hydrocarbon radicals, such as alpha-N-methyl-pyrrolidone and alpha- N-methylpiperidone are also suitable.

As amines there may be used primary, secondary or tertiary amines. Those of the aliphatic series are especially suitable, in particular those of which the alkyl group contains 1 to 6 carbon atoms. Such amines are for example methylamine, ethylamine, propylamine,.nor-v mal-butylamine, hexylamine; also dimethylamine, diethyl atent O amine, di-normal-butylamine, diisopropylamine, dibutylamine, methylethylamine, .ethylbutylamine, trimethylamine, triethylamine, tripropylamine and tributylamine.

Higher molecular weight. aliphatic amines, as, for example ethylhexylamine and di-(Z-ethylhexylamine) are also suitable. There also come into question primary,

tertiary amines of the said series. may be mentioned: cyclohexylamine, dicyclohexylamine,

tricyclopentylamine, benzylamine, aniline, methylaniline,,,

dimethylaniline, diethylaniline, propylaniline, N-methylcyclohexylamine and N-ethylcyclohexylamine.

free from olefinic double linkages.

The adding on of chlorine to acrylic. acid esters, for example esters of saturated aliphatic, cycloaliphatic or araliphatic alcohols, is preferably effected by incorporating in the ester vapor, the vapor of the substituted acid amide or amine and/or a mixture of these compounds, in a small amount for example 0.1 to 5% by weight, ad} vantageously about 0.1 to 3% by weight with reference to the ester, and then bringing the mixture together with chlorine. The amount of chlorine is chosen approxi mately so that there is about 0.9 to 1.5 mols of chlorine to each mol of ester. In order to avoid the polymerization of the acrylic ester during the reaction it is possible to co-employ polymerization retarders, as for example.

hydroquinone or hydroquinone monomethyl ether.

The most favorable reaction temperatures are dilferent for the individual esters and may be determined easily by preliminary experiment. In general they lie between, about and 200 C. Since the reaction proceedsv exothermically, a supply of heat externally is usually unnecessary, but rather cooling is usually necessary to lead away excess heat of reaction because otherwise the reaction proceeds too violently.

For carrying out the reaction it is of advantage to use a corrosion-proofreaction tube which ispreferably charged with filler bodies, as for example of glass or porcelain, which wholly or partly fill the tube. It is pos-' sible to work in,cocurrent: or countercurrent. It is especially simple and preferable to lead the vaporous substances to be reacted downwardly. in cocurrent through the tube.

The liquid fraction of the alphabetadichlorpropionic acid ester can be condensed from the reaction mixture leaving the reaction tube and separated in the usual way, for example by distillation; if desired after extraction or washing out-ofthe added substance, for example the amine by washing withacidified water.

The following examples. will further illustrate this invention but the invention is not restricted to these examples.

Example 1- 100 grams per'hourof a; vaporous mixture of 2,200 grams of. acrylic acid: methyl ester'stabilized with 0.1% of hydroquinoneand 22 grams of N-methylpyrrolidone are led downwardly at 95 C. through a porcelain tube 400 mm. long and 40- mm. in diameter. At the same time grams of chlorine per hour are supplied to the top of the tube. The heat of" reaction set free is carried away by cooling" with water. The reaction mixture Patented Nov. 19,. 1957 Finally other amines thanthose specified may be used which are.

3 with reference to the acrylic acid ester reacted is 94% of the theoretical yield.

Example 2 .A vaporous mixture of 2,200 grams of methyl acrylate stabilized with 0.1% of hydroquinone and 44 grams of N,N-diethylformamide are led at such a speed through the reaction tube described in Example 1 that 100 grams of the mixture enter the tube each hour. At the same time there are supplied to the tube 90 grams of chlorine per hour. The reaction is carried out at a temperature of 85 C., and care is taken by cooling the reaction tube that the said temperature is not exceeded by the reaction heat set free.-

From the liquid reaction product obtained by condensation, there are obtained by fractional distillation 3,780 grams of alpha-beta-dichlorpropionic acid methyl ester. 264 grams of products of higher boiling point are obtained. The yield of a1pha-beta-dichlorpropionic acid methyl ester. amount to 94% of the theoretical yield with reference to the methyl acrylate reacted.

Example 3 A vaporous mixture of 2,200 grams of methyl acrylate stabilized with 0.1% of hydroquinone and 44 grams of N.N-dimethylformamide are led at such a speed through the reaction tube described in Example 1 that 100 grams of the mixture enter the tube each hour. At the same time there are supplied to the tube 90 grams of chlorine per hour. The reaction is carried out at a temperature of 85 C., and care is taken by cooling the reaction tube that the said temperature is not exceeded by the reaction heat set free.

From the liquid reaction product obtained by condensation, there are obtained by fractional distillation 3,804 grams of alpha-beta-dichlorpropionic acid methyl ester. 238 grams of products of higher boiling point are obtained. The yield of alpha-beta-dichlorpropionic acid methyl ester amounts to 95.5% of the theoretical yield with reference to the methyl acrylate reacted.

Example 4 100 grams of a vaporous mixture of 2,200 grams of methyl acrylate stabilized with 0.1% of hydroquinone and 22 grams of dimethylamine are led per hour downwardly through a reaction tube described in Example 1 at 85 C. At the same time 100 grams of chlorine per hour are supplied to the top of the reaction tube. The reaction heat set free is carried away by cooling with water. The reaction mixture leaving the tube at the bottom is led to a condenser. The liquefied fraction is fractionally distilled. After the whole of the ester has been passed through, there are obtained, besides 75 grams of unreacted methyl acrylate and 250 grams of products of higher boiling point, 3,645 grams of alpha-beta-dichlorpropionic acid methyl ester. The yield of this ester is 94% of the theoretical yield with reference to reacted methyl acrylate.

Example 5 A vaporous mixture of 2,200 grams of methyl acrylate stabilized with 0.1% of hydroquinone and 22 grams of diethylamine is led through the reaction tube described in Example 1 at such a speed that 100 grams of the mixture enter the tube per hour. At the same time 90 grams of chlorine per hour are supplied to the tube. The reaction is carried out at a temperature of 95 C., care being taken by cooling the reaction tube that the said temperature is not exceeded by the reaction heat set free.

From the liquid reaction product obtained by condensation, 3,780 grams of alphabeta-dichlorpropionic acid methyl ester and 35 grams of methyl acrylate are obtained; 240 grams of products of higher boiling point are obtained. The yield of alpha.beta-dichlorpropionic acid the mixture enter the tube per hour.

I 4 methyl ester amounts to 95.5% of the theoretical yield with reference to acrylic ester reacted.

Example 6 A vaporous mixture of 2,200 grams of methyl acrylate stabilized with 0.1% of hydroquinone and 22 grams of normal-butylamine is led through the reaction tube described in Example 1 at such a speed that 100 grams of At the same time 90 grams of chlorine are supplied to the tube per hour. The reaction is carried out at a temperature of C., care being taken by cooling the reaction tube that the said temperature is not exceeded by the reaction heat set free. The reaction product is worked up as in Example 1.

With a quantitative conversion of the methyl acrylate, there are obtained 3,840 grams of alpha.beta-dichlorpropionic acid methyl ester and 265 grams of products of higher boiling point. The yield is 96% of the theoretical yield.

Example 7 care being taken by cooling the reaction tube that the said temperature is not exceeded by the reaction heat set free. The reaction product is worked up as in Example 1.

65 grams of unreacted methylacrylate, 3,660 grams of alpha.beta-dichlorpropionic acid methyl ester and.

305 grams of products of higher boiling point are obtained. The yield of alpha.beta-dichlorpropionic acid methyl ester amounts to 94% of the theoretical yield with reference to methyl acrylate reacted.

Example 8 A vaporous mixture of 2,200 grams of acrylic acid methyl ester stabilized with 0.1% of hydroquinone and 30 grams of n-methyl formamide is led downwardly at C., at a rate of 100 grams per hour, through a reaction tube described in Example 1. At the same time 90 grams of chlorine are fed into the reaction tube per hour from its top end. The reaction heat set free is carried away by cooling with water. The reaction mixture leaving at the bottom end of the tube is led through a condenser and the liquefied fraction is fractionallydistilled.

From the whole amount of the ester feed 3,730 grams of alpha.beta-dichloropropionic acid methyl ester and, in addition, 298 grams of products of higher boiling point are obtained. The yield of alpha.beta-dichloropropionie acid methyl ester is 93% of the theoretical yield with reference torthe acrylic acid methyl ester feed.

Example 9 A vaporous mixture of 2,200 grams of acrylic acid methyl ester stabilized with 0.1% of hydroquinone, and 36 grams of N.N-dibutyl formamide is passed through a reaction tube of the type described in Example 1 at a rate of 100 grams per hour. At the same time 90 grams of chlorine are fed into the reaction tube per hour from its top end. The reaction is carried out at a temperature of C. The liquid reaction product obtained by condensation is subjected to fractional distillation, 128 grams of unreacted acrylic acid methyl ester and 254 grams of higher boiling products being obtained in addition to 3,490 grams of alpha.beta-dichloropropionic acid methyl ester. The yield of the said ester amounts to 92.5% of the theoretical yield with reference to the reaction.

Example 10 A vaporous mixture of 2,200 grams of acrylic acid methyl ester stabilized with 0.1% of hydroquinone, and 36 grams of 2-ethylhexylamine-(1) is passed through a reaction tube of the type described in Example 1 at a rate of 100 grams per hour. At the same time 90 grams of chlorine are fed into the reaction tube per hour from its top end. The reaction is carried out at a temperature of 100 C. The liquid reaction product obtained by condensation is subjected to fractional distillation, 127 grams of unreacted acrylic acid methyl ester and 275 grams of higher boiling fractions being obtained in addition to 3,413 grams of alpha.beta-dichloropropionic acid methyl ester. The yield of the said ester is 90.5% of the theoretical yield with reference to the amount of acrylic acid methyl ester which went into reaction.

What we claim is:

1. A process for the production of alpha.beta-dichlorpropionic acid esters by addition of chlorine on acrylic acid esters in the gas phase at temperatures from 80 to 200 C. which comprises carrying out said reaction in the presence of from 0.1 to 5% by weight, with reference to the amount of the acrylic acid ester feed, of an organic nitrogen containing compound selected from the group consisting of N-alkyl substituted amides of a lower saturated aliphatic carboxylic acid in which the N-substituents are lower alkyl groups up to 4 carbon atoms, cyclic N-methyl substituted amides and amines derived from aliphatic saturated hydrocarbons.

2. The process as claimed in claim 1 wherein the organic nitrogen compound used is N.N-dimethylformamide.

3. The process as claimed in claim 1 wherein the organic nitrogen compound used is N.N-diethylformamide.

4. The process as claimed in claim 1 wherein the organic nitrogen compound used is diethylamine.

5. The process as claimed in claim 1 wherein the organic nitrogen compound used is triethylamine.

6. The process as claimed in claim 1 wherein the organic nitrogen compound used is n-butylamine.

References Cited in the file of this patent UNITED STATES PATENTS 2,647,923 Burton Aug. 4, 1953 2,680,764 Ney June 8, 1954 2,774,785 Wystrach Dec. 18, 1956 

1. A PROCESS FOR THE PRODUCTION OF ALPHA BETA-DICHLORPROPIONIC ACID ESTERS BY ADDITION OF CHLORINE ON ACRYLIC ACID ESTERS IN THE GAS PHASE AT TEMPERATURES FROM 80* TO 200*C. WHICH COMPRISES CARRYING OUT SAID REACTION IN THE PRESENCE OF FROM 0.1 TO 5% BY WEIGHT, WITH REFERENCE TO THE AMOUNT OF THE ACRYLIC ACID ESTER FEED, OF AN ORGANIC NITROGEN CONTAINING COMPOUND SELECTED FROM THE GROUP CONSISTING OF N-ALKYL SUBSTITUTED AMIDES OF A LOWER SATURATED ALIPHATIC CARBOXYLIC ACID IN WHICH THE N-SUBSTITUENTS ARE LOWER ALKYL GROUPS UP TO 4 CARBON ATOMS, CYCLIC N-METHYL SUBSTITUTED AMIDES AND AMINES DERIVED FROM ALIPHATIC SATURATED HYDROCARBONS. 